Measurement System Analysis (MSA) Flashcards

A Gage R&R study was performed on a critical measurement system. The results showed the % Contribution for the total Gage R&R was 8% and the number of distinct categories (ndc) was 7. Based on common industry guidelines, what is the most appropriate conclusion?

Answer: The measurement system is acceptable for its intended use.

According to Automotive Industry Action Group (AIAG) guidelines, a measurement system is generally considered acceptable if the % Contribution is less than 9% (or % Study Variation is less than 10%). Additionally, a number of distinct categories (ndc) of 5 or greater is acceptable. Since the results (8% contribution and ndc of 7) both fall within the acceptable ranges, the system is considered adequate.

In Measurement System Analysis, what does 'reproducibility' evaluate?

Answer: The variation that occurs when different appraisers measure the same part using the same gage.

Reproducibility, often called appraiser variation, is the variation in the average of the measurements made by different appraisers using the same measuring instrument when measuring the identical characteristic on the same part. Repeatability is variation from the same appraiser. Bias is the difference from a master value. Linearity is the change in bias over the operating range.

A Six Sigma team needs to determine if their measurement system is accurate. They have several parts with known, traceable master values. Which of the following MSA tools is specifically designed to assess accuracy by comparing measurements to a known standard across the operating range?

Answer: A Gage Linearity and Bias Study

A Gage Linearity and Bias Study is used to assess the accuracy of a measurement system. Bias determines how close the measurements are to a reference value, while linearity assesses if that accuracy remains consistent across the range of expected measurements. A Gage R&R study assesses precision (repeatability and reproducibility), not accuracy.

An Attribute Agreement Analysis was conducted for a visual inspection process. The results show a high 'Between Appraisers' agreement (95%), but a low 'All Appraisers vs. Standard' agreement (70%). What is the most likely root cause for this issue?

Answer: The appraisers are using a flawed or poorly understood operational definition for inspection.

High agreement between appraisers indicates they are consistent with each other. However, low agreement with the expert standard means they are consistently getting the wrong answer together. This points to a systemic problem, most likely that the operational definition of what constitutes a 'good' or 'bad' part is unclear, ambiguous, or has been misinterpreted by the entire group.

To ensure that data collected for a process improvement project is trustworthy, a Measurement System Analysis (MSA) should be performed. In which phase of the DMAIC methodology is this activity most critically and typically completed?

Answer: Measure

MSA is a critical component of the Measure phase. Before a team can analyze process data to draw conclusions, they must first verify that the data is reliable and that the measurement system itself is not a significant source of variation. Performing MSA in the Measure phase ensures the validity of all subsequent data analysis.

A Gage R&R study on a new digital caliper resulted in a number of distinct categories (ndc) of 2. What is the most practical implication of this result for process control?

Answer: The measurement system can only differentiate between two groups of parts (e.g., 'in-spec' and 'out-of-spec').

The number of distinct categories (ndc) indicates how many separate groups of parts the measurement system can distinguish within the observed process variation. An ndc of 2 means the system can only effectively divide the parts into two groups, such as high/low or pass/fail, and is not sensitive enough for detailed process control or analysis. An ndc of less than 5 is generally considered unacceptable.